Knoxville joined Babcock on the TMZ Sports show on FS1 ... where he said he's champing at the bit to settle the score between him and Sami.

"I can't wait to get to Dallas to slap Sami Zayn in his stupid face," Johnny says.

Of course, the feud between Knoxville and Zayn has been going on for months. When Knoxville made his WWE debut recently, he challenged Zayn to a match.

Zayn denied Johnny's request ... telling him he had no business being in the WWE. Knoxville exacted some revenge when he cost Zayn the intercontinental title against Ricochet on Smackdown a few weeks ago -- setting the stage for their showdown next week.

Knoxville, the ultimate prankster, predicted the worst is yet to come for Zayn when the two fight at WWE's crowning spectacle in an "anything goes" match.

FYI, "anything goes" means the standard rules and stipulations governing a typical WWE fight are out of play.

But, the "Jackass" star isn't taking his fight with the pro-wrestler lightly ... he says he's been training and working with a wrestling coach to hold his own in the ring.

Knox took things a step further in their bitter rivalry when he used a plane banner to blow up the Champ's phone number (which hasn't stopped ringing since) for all of L.A. to see.

Knox made it abundantly clear he's got one goal -- to retire Sami Zayn.